I. Field of the Invention
The present invention relates generally to a speed control circuit for an electric and, more particularly, to such a speed control circuit which is employed in a louvered sign assembly.
II. Description of the Prior Art
Louvered sign assemblies, such as that disclosed in U.S. Pat. No. 3,313,131 to Willy T. Werner on Apr. 11, 1967, are widely employed in retail establishments and the like. Such louvered sign assemblies typically comprise a rectangular frame having a plurality of louvers rotatably mounted to the frame so that the louvers are spaced apart and parallel to each other. Furthermore, each louver typically is triangular in crossectional shape and has a portion of an advertising message on each of its three sides.
Thus, in operation, the louvers are rotatably driven so that one face of all the louvers are substantially coplanar with each other thereby displaying an advertising message. After a predetermined period of time, the louvers are rotated 120.degree. so that a second side of all of the louvers are coplanar with each other thus displaying a different advertising message and so on. Consequently, the louvered sign assembly is capable of displaying three distinct advertising messages in a sequential fashion.
One problem with these previously known louver sign assemblies is that it is relatively difficult to control the rotational speed of the louvers as they are rotated between their three angular positions. In some applications, a high rate of speed creates damage and undue wear and tear on the sign assembly, as well as the motor, thus requiring frequent and expensive repairs. Furthermore, in some cases, a low rotational speed of the louvers in the sign assembly is desired for a particular advertising effect.
Previously, there has been no previously known speed controls for a louver sign assembly which is capable of controlling the motor speed between very low and very high speeds and which also provide a soft starting and soft stopping for the motor.